PLC-2 conversion to Micrologix

I replaced a PLC-2 Mini with a Logix 1100. I uploaded the PLC-2 code and converted it into Logix500. The program does not work! I found a few things that I could not understand: PLC-2 is using two physical outputs that are not wired but are used in the code as conditions. A number of physical output addresses that have no hardware assigned are used for code but then not re-used anywhere in the code.
I uploaded the program with a software provided by www.usconverters.com
I then wrote line by line into Logix500 using the same addressing as PLC-2 - then assigned the physical addresses and B3 bits to internal bits, timers etc. Code looked simple but it is not working right.
Why would they use physical output addresses instead of memory bits for logic.
I need to understand this to make the logic work.

ThomasGruetter said:

Why would they use physical output addresses instead of memory bits for logic.
I need to understand this to make the logic work.

Click to expand...

Probably an economy thing. If word 110 was used for an input module that left 010 unusable for real outputs. There were sixteen perfectly good bits available for latches, etc. Some of the PLC-2s I worked on used word 170 as a constant of zero, since the rack power supply occupied the far right slot and none of the input bits could ever be turned on.

in the PLC2's the lower memory 0-77 are used for outputs and 100-177 are used for inputs but then can be used as program memory if they are not needed for the I/O
also timers and counters use 2 words 100 apart from each other. timer address 200 will use both address 200 and 300 . there are no safe guards to prevent you from overwriting the addresses and corrupting the data. the addressing is Octal 0-7 10-17 not 8 or 9 in the memory

Okay - where I'm still puzzled...
I have 110, 111, 112 words for inputs.
My output word is 010 I believe but also words 011 012 and 013 are used in the logic. Some of these addresses are turned on as outputs but not used again in the logic.
Is it possible that 013 word is for the real outputs??

Do you have any of the original program documentation - schematics, program listings, address comments, wire numbers?

word 013 would be output on rack 1
if there is no rack then the bits could be used in the program

I would recommend that you zip and attach your programs for the plc2 and the Micrologix 1100 to this thread. Try to also print them out either to a PDF or text file for those that don't have software.

Actually
011 in rack 1 slot 1
012 is rack 1 slot 2
013 is rack 1 slot 3
racks are 1-7 but a rack can be split in 2 depending on the dip switches
inputs and outputs can be addressed as bits or words
block transfer depending on the modules are addressed as words

Still not 100% clear about the addressing.
I have 16 point input modules in slot 1,2,3 and assume address words are 110,111,112.
My suspicion is that the address word for the output module in slot 4 is 013 ?
That would make sense as most the bits of this word are not used in the program again.

Then what is the output input designation for? I will use the 013 word for my physical outputs and try again. This seems to make sense now...
Thanks for all the support.

0 = Output
1 = Input
2-7 = data table
Racks start at 1 - 7 Max 7 Racks on PLC2's
if you are using address 110 then that would be Input Rack 1 Slot 0
111 would be Input Rack 1 Slot 1
112 would be Input Rack 1 Slot 2
The addressing on the PLC2's is tricky you can have a Single slot rack, or 2 slot rack or 2 half racks depending in the configuration selected by the dip switches in the rack
the data table doesn't change but data you use dos.
I have seen 1 14 slot rack look like just 1 rack or 2 racks as far as the program goes but if you look at it you will just see the 1 rack.
in the mini's they sometimes put a power supply in a slot if they don't need a lot of power
post copies od the code along with pictures of the rack maybe we can figure out exactly what you have.
the data table is predefined and stays the same for all racks just some words are not used for I/O but they can be used in the program if needed.

Conclusion:
The addressing was the problem:
Input words: 110, 111, 112 and so on
Output words: 010, 011, 012, 013
I have 4 racks : #1, 16-Input = word 110
#2, 16-Input = word 111
#3, 16-Input = word 112
#4, 16-Output= word 013
As all my output words 010, 012 etc. were used in the logic and I assumed the first one would be for the output card. It's use of bits matched my physical connections.
So 1st digit: 1= input, 0= output
2nd digit: rack #
3rd digit: slot #
Hope this helps someone in the future....Great support from online members - Cheers

ThomasGruetter said:

Still not 100% clear about the addressing.
I have 16 point input modules in slot 1,2,3 and assume address words are 110,111,112.
My suspicion is that the address word for the output module in slot 4 is 013 ?
That would make sense as most the bits of this word are not used in the program again.

Then what is the output input designation for? I will use the 013 word for my physical outputs and try again. This seems to make sense now...
Thanks for all the support.

Click to expand...

There is a misunderstanding here, for sure.
One place to start is with the language.
A CHASSIS is a physical place where modules are.
A RACK is a logical thing representing modules. *NOTE: I did not say that a logical rack represents a physical chassis...'cause it doesn't.

The old days PLC-2 (and the 5) could do a trick called Complimentary I/O, whereby the I/O image table could be maximized. Understand that the I/O structure is defined by the hardware, DIP switches, and such. Simply having the software is no description of the physical world.
Good Luck.